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RESPIRATORY INFECTIONS
Upper Respiratory Tract Infections
Lower Respiratory Tract Infections
1. COMMUNITY ACQUIRED PNEUMONIA (CAP)
1. COMMUNITY ACQUIRED PNEUMONIA (CAP)
The diagnosis of CAP generally requires the demonstration of an infiltrate on chest radiograph in a patient with a clinically compatible syndrome (E.g.: fever, dyspnoea, cough and sputum production).
Previous relevant encounters at any health care facilities and antibiotic exposure must be obtained.
Pulmonary tuberculosis (PTB) must be considered and further investigated in an appropriate clinical situation such as prolonged symptoms, presence of risk factors for PTB and radiological changes compatible with PTB.
Choice of antibiotic treatment must also be based on likely etiology and local antibiogram whenever possible.
Assessment of severity and decision for admission can be guided by using CURB-65 or SMART-COP scoring. Physician should use the scoring tools to support, not to replace clinical judgment.
CURB-65 and SMART-COP scoring
CURB-65 criteria
Confusion (new onset)
Urea > 7 mmol/l
Respiratory rate of ≥ 30/min
Blood pressure ≤ 90/60 mmHg
Age ≥ 65
CURB-65 score
Score 0-1: Mild. Can manage outpatient.
Score 2: Moderate. Consider admission.
Score 3-5: Severe. Inpatient admission. Consider ICU referral.
Alternatively, CRB-65 can also be used. It does not require laboratory values for its calculation, and the score value interpretation is the same as for CURB-65.
SMART-COP criteria
Systolic BP < 90mmHg (2 points)
Multilobar CXR involvement (1 point)
Albumin <3.5 g/dL (1 point)
Respiratory rate ≥ 30/min (≥ 25/min if ≤50 yrs old) (1 point)
Tachycardia ≥ 125/min (1 point)
Confusion (new onset) (1 point)
Oxygen saturation (2 points)
If age >50: SpO2 ≤90% OR PaO2<60 or PF ratio <250
If age ≤50: SpO2 ≤93% OR PaO2<70 or PF ratio <333
Arterial pH <7.35 (2 points)
SMART-COP score
Score 0-2: Mild. Can manage outpatient.
Score 3-4: Moderate. Inpatient admission.
Score ≥5: Severe. Consider ICU referral.
1.1 Outpatient
Preferred
Amoxicillin 500mg-1g PO q8h for 5-7 days
Alternative
Doxycycline 100mg PO q12h for 5-7 days
Comments
--
1.2 Outpatient (With Comorbidities)
Preferred
Amoxicillin/clavulanate 625mg PO q8h for 5-7 days
MAY ADD
*Azithromycin 500mg PO q24h for 3 days
OR
*Doxycycline 100mg PO q12h for 5-7 days
Alternative
Antibiotic allergy:
**Levofloxacin 750mg PO q24h for 5 days
Comments
Comorbidities: Chronic heart, lung, liver, or renal disease, diabetes mellitus, alcoholism, malignancy, or asplenia.
*If atypical pathogen is suspected (E.g.: extrapulmonary manifestations and diffuse infiltrations radiologically).
**Levofloxacin should be strictly reserved for antibiotic allergy due to higher risk of adverse events.
Refer to Appendix 3 for antibiotic allergy.
1.3 Inpatient - Moderate CAP
CURB-65 Score 2 or SMART-COP Score 3-4
Preferred
Amoxicillin/clavulanate 1.2g IV q8h for 5-7 days
MAY ADD
*Azithromycin 500mg IV/PO q24h for 3 days
OR
*Doxycycline 100mg PO q12h for 5-7 days
Alternative
Ceftriaxone 2g IV q24h for 5-7 days
MAY ADD
*Azithromycin 500mg IV/PO q24h for 3 days
Antibiotic allergy:
**Levofloxacin 750mg IV/PO q24h for 5-7 days
Comments
*If atypical pathogen is suspected (E.g.: extrapulmonary manifestations and diffuse infiltrations radiologically). May need a longer duration of therapy among immunocompromised patients or those with confirmed Legionella pneumonia.
**Levofloxacin should be strictly reserved for antibiotic allergy due to higher risk of adverse events.
To switch to oral therapy when clinical condition improves and patient is able to tolerate orally.
If suspected melioidosis infection, refer to Tropical Infection section.
1.4 Inpatient - Severe CAP
CURB-65 score ≥ 3 or SMART-COP score ≥ 5
Preferred
Amoxicillin/clavulanate 1.2g IV q8h for 5-7 days
MAY ADD
*Azithromycin 500mg IV/PO q24h for 3 days
OR
*Doxycycline 100mg PO q12h for 5-7 days
Alternative
If at risk of pseudomonal infection:
**Piperacillin/tazobactam 4.5g IV q6-8h for 7 days
OR
Cefepime 2g IV q8h for 7 days
MAY ADD
*Azithromycin 500mg IV/PO q24h for 3 days
Comments
Strong risk factors for pseudomonal infection:
Prior respiratory infection or isolation of Pseudomonas aeruginosa
Hospitalization with receipt of IV antibiotics in past 3 months
Detection of gram-negative rods on a good-quality sputum gram stain
Other risk factors for pseudomonal infection:
Recent hospitalization or stay in a long-term care facility
Recent antibiotic use
Frequent COPD exacerbations requiring glucocorticoid/antibiotic
Structural lung diseases (E.g.: bronchiectasis)
Immunosuppressed
*If atypical pathogen is suspected (E.g.: extrapulmonary manifestations and diffuse infiltrations radiologically). May need a longer duration of therapy among immunocompromised patients or those with confirmed Legionella pneumonia.
**Piperacillin/tazobactam: if given as q8h, to be given as extended infusion (over 3-4 hours)
IV Ceftazidime is not recommended for empirical therapy due to poor activity against Streptococcus pneumoniae. If suspected melioidosis infection, refer to Tropical Infections section.
2. VIRAL PNEUMONIA
2. VIRAL PNEUMONIA
2.1 COVID-19
2.2 Influenza
Preferred
Oseltamivir 75mg PO q12h for 5 days
Alternative
*Baloxavir
40-80kg: 40mg PO single dose
≥80kg: 80mg PO single dose
Comments
Clinical benefit is greatest if initiated within 48 hours.
In hospitalized / immunocompromised patients, treatment is started regardless of symptom duration, and may need longer duration of treatment.
*Not listed in MOH Drug Formulary.
2.3 Varicella Zoster
Preferred
Acyclovir 10mg/kg IV q8h for 7 days
Alternative
--
Comments
--
3. LUNG ABSCESS AND EMPYEMA
3. LUNG ABSCESS AND EMPYEMA
3.1 Empirical treatment
Preferred
No recent thoracic surgery/ procedure or HAP/VAP:
Amoxicillin/clavulanate 1.2g IV q6-8h
OR
Ampicillin/sulbactam 3g IV q6h
Post-procedure (E.g. pleural interventions, thoracic or oesophageal surgery) or presence of HAP/VAP:
*Piperacillin-tazobactam 4.5g IV q6-8h
OR
Cefepime 2g IV q8h
PLUS
Metronidazole 500mg IV q8h
MAY ADD **Vancomycin 15-20mg/kg (actual body weight) IV q8-12h; not to exceed 2g/dose
Alternative
No recent thoracic surgery/ procedure or HAP/VAP:
Ceftriaxone 2g IV q24h
PLUS
Metronidazole 500mg IV q8h
Antibiotic allergy:
Clindamycin 600mg IV/PO q8h
Post-procedure (E.g. pleural interventions, thoracic or oesophageal surgery) or presence of HAP/VAP:
Meropenem 1g IV q8h
MAY ADD
**Vancomycin 15-20mg/kg IV q8-12h
Comments
Duration of treatment:
Adequate source control: 2-4 weeks of antibiotics from the time of drainage/surgery and defervescence.
Inadequate source control: 4-6 weeks of antibiotics.
Lung empyema: Attempts should be made to drain the collection to improve clinical outcome.
Change to oral regime once clinical improvement is seen. Refer to Appendix 6 for IV to PO switch.
Avoid aminoglycosides in the management of empyema.
*Piperacillin/tazobactam: if given as q8h, to be given as extended infusion (over 3-4 hours).
**MRSA coverage is to be based on local hospital MRSA prevalence. Refer to Appendix 1 for vancomycin dose.
If melioidosis is suspected, refer to Tropical Infection section.
Refer to Appendix 3 for antibiotic allergy.
3.2 Methicillin-susceptible Staphylococcus aureus (MSSA)
Preferred
Cloxacillin 2g IV q4h
Alternative
Cefazolin 2g IV q8h
Comments
Duration: 4-6 weeks, depending on clinical response. In rare cases (slow response to antibiotics) may need prolonged therapy.
Change to oral therapy (E.g. Amoxicillin/clavulanate 625mg PO q8h or cephalexin 1g PO q6h) to complete the duration once patient stabilized and improved.
4. INFECTIVE EXACERBATION OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD)
4. INFECTIVE EXACERBATION OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD)
Antibiotics only considered if there is:
Increased purulence in sputum AND one of the following:
Increased sputum volume
Increased dyspnoea
OR
Patient intubated
4.1 Outpatient
Preferred
Amoxicillin/clavulanate 625mg PO q8h for 5 days
Alternative
Cefuroxime 500mg PO q12h for 5 days
OR
Doxycycline 100mg PO q12h for 5 days
Comments
--
4.2 Inpatient
Preferred
Amoxicillin/clavulanate 1.2g IV q8h for 5-7days
MAY ADD
Azithromycin 500mg IV/PO for 3 days
Alternative
Ceftriaxone 2g IV q24h for 5-7 days
MAY ADD
Azithromycin 500mg IV/PO for 3 days
Comments
--
4.3 Inpatient with Risk Factor of Pseudomonal Infection
Preferred
*Piperacillin-tazobactam 4.5g IV q6-8h for 7 days
MAY ADD
Azithromycin 500mg IV/PO for 3 days
Alternative
Cefepime 2g IV q8h for 7 days
MAY ADD
Azithromycin 500mg IV/PO for 3 days
Comments
Risk factors for pseudomonal infection:
Chronic colonization of previous isolation of Pseudomonas aeruginosa from sputum
Very severe COPD (FEV1<30% predicted)
Bronchiectasis
Broad spectrum antibiotic use within the past 3 months
Chronic systemic glucocorticoid use
*Piperacillin/tazobactam: if given as q8h, to be given as extended infusion (over 3-4 hours)
5. HOSPITAL ACQUIRED PNEUMONIA (HAP/VAP)
5. HOSPITAL ACQUIRED PNEUMONIA (HAP/VAP)
Risk factors for multidrug-resistance (MDR) organisms HAP/VAP:
Prior intravenous antibiotic use within 90 days
Previous colonization or infection with MDR pathogens
Additional risk factors for MDR organisms VAP:
Septic shock at time of VAP
Acute respiratory distress syndrome (ARDS) or acute renal replacement therapy (RRT) preceding VAP
≥ 5 days of hospitalization prior to onset of VAP
HAP: Pneumonia that occurs ≥ 48 hours after admission and did not appear to be incubating at the time of admission
VAP: Pneumonia that occurs ≥ 48 hours after endotracheal intubation
5.1 Early Onset HAP/VAP
2 - 4 days of admission/intubation
Preferred
Amoxicillin/clavulanate 1.2g IV q8h for 5-7days
Alternative
Ceftriaxone 2g IV q24h for 5-7 days
Comments
Need to adjust to local antibiogram/ prevalent organisms.
Consider broader spectrum antibiotic if deteriorated while on adequate antibiotic therapy.
5.2 Late Onset HAP/VAP OR Severe Pneumonia OR At Risk of Pseudomonal Infection
Late onset HAP/VAP: 5 days or more of admission/intubation
Preferred
*Piperacillin-tazobactam 4.5g IV q6-8h for 7 days
OR
Cefepime 2g IV q8h for 7 days
Alternative
High risk of MDR organisms:
Meropenem 1g IV q8h for 7 days
OR
Imipenem/cilastatin 500mg IV q6h for 7 days
Comments
Refer to CAP section for Risk of Pseudomonal Infection.
Severe pneumonia:
Septic shock
Respiratory failure, need for ventilation support
Rapid progression of infiltrates on chest X-ray
Ideal empirical antibiotic coverage depends on local prevalence of organisms. To de-escalate antibiotics according to culture and sensitivity results.
Longer duration may be indicated depending upon clinical, radiological and laboratory parameters.
*Piperacillin/tazobactam: if given as q8h, to be given as extended infusion (over 3-4 hours).
6. ASPIRATION PNEUMONIA
6. ASPIRATION PNEUMONIA
It is important to distinguish aspiration pneumonia from aspiration events/ aspiration pneumonitis.
Aspiration pneumonia: a bacterial infection caused by aspiration of organisms from oropharynx.
Aspiration (chemical) pneumonitis: acute chemical injury to the lung parenchyma after aspiration of acidic stomach contents. Antibiotic is not indicated.
Indications of antibiotic therapy:
Delayed symptoms (suggestive of aspiration pneumonia, as compared to rapid onset within hours in pneumonitis)
Patients taking gastric acid suppression therapy or with bowel obstruction
Preferred
Amoxicillin/clavulanate 1.2g IV q8h
Alternative
Ceftriaxone 2g IV q24h
MAY ADD
*Metronidazole 500mg IV q8h
Antibiotic allergy:
Clindamycin 600mg IV/PO q8h
Comments
Duration: 7 days
*Anaerobic coverage is not routinely required for suspected aspiration pneumonia unless lung abscess or empyema is suspected.
To switch to oral therapy when clinical condition improves and patient is able to tolerate orally.
References:
Metlay JP, Waterer GW, Long AC, et al. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019;200(7):e45-e67. doi:10.1164/rccm.201908-1581ST
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Global Initiative for Chronic Obstructive Lung Disease – Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease (2023 REPORT)
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Clinical Practice Guidelines by the Infectious Disease Society of America : 2018 Update on DIagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenza
Clinical Practice Guidelines for Influenza WHO 2024
NICE Guideline: Pneumonia (community and hospital-acquired): Antimicrobial Prescribing. 2019.
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Torres A, Niederman MS, Chastre J, et al. International ERS/ESICM/ESCMID/ALAT guidelines for the management of hospital-acquired pneumonia and ventilator-associated pneumonia. Eur Respir J 2017; 50: 1700582
Tamma PD, Aitken SL, Bonomo RA, Mathers AJ, van Duin D, Clancy CJ. Infectious Diseases Society of America Antimicrobial-Resistant Treatment Guidance: Gram-Negative Bacterial Infections. Infectious Diseases Society of America 2023; Version 3.0. Available at https://www.idsociety.org/practice-guideline/amr-guidance/. Accessed 16 August 2023
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